Protective device for electrical systems.



UNITED STATES PATENT OFFICE.

KARL KUHLMANN, OF BERLIN, PANKOW, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEfICE FOR ELECTRICAL SYSTEMS.

Specmcation of Letters Patent.

Patented Aug. 25, 1908.

Application filed March '15, 1907. Serial No. 362,479.

To all whom it may concern:

Be it known that I, KARL KUiiLMANx, a

at erlin, Pankow, Germany, have invented certain new and useful Improvements in Protective Devices for Electrical Systems, of which the following is a specification.

In electrical supply systems, spark gaps or condensers are generally employed as a protection against excessive potentials. They are usually connectedin series with resistances, and arranged partially between the leads themselves and partially between their respective leads and ground. Attempt has heretofore been made to reduce the. number of resistances, but too little attention has:

heretofore been paid to the point of creating excess potential paths according 'to the frequency of the excess potentials. The number of oscillations is of essential influence on the path selected by a quantity of. electricity.

for its discharge. Thus, for example, it is .known that high frequency discharges choose sistances.

In Fig. 1 thc three conductors 1, and 3 of a three phase system to be protected, are

connected to each other through resistances 4, 5 and 6, each connected in series with a safet device such as the spark gaps 7, 8, and 9. ach conductor of the three'phase system is separated from every other conductor bya resistance and a safety device or spark gap, and the spark gaps and resistances are.

so dis osed that each conductor is connected direct y to the spark gap of onepath and the resistance of another ath. At the junction points 1.0, 11 and 12, etween thespfety devices and their respecti resistances, auxili paths are connected which lead through spar gaps 13, 14 and 15 and resistances. 16, 17 an 18 to a junction point 19 connected 'der some circumstances, be omitted.

and 1'8 are comparatively small and may, un-

this arrangement of the resistances and spark gaps, excessive potentials of comparatively small frequency which may be produced between any lead-and earth, lind a path of discharge through a resistance and its spark gap, for example, from conductor 2 through resistance 4, spark gap 1.3-, and resistance 16',

to earth; the high frequency discharges choose on the contrary, the path through spark gap 8, spark gap 14, and resistance 17 for the reason thatthis path contains only small resistance. In the latter case, however, the iirst mentioned path is also partly utilized. The arrangement has the great advantage that lightning discharges, generally large, are not merely carried off through a single spark gap but are carried toearth ontwo parallel paths disturbances of the safety device by reason of too great heating is therefore avoided. Excessive potentials between two conductors, for example, between conductors 2 and 1, select, according tothe number of oscillations, the path through 4 and 7, or through 8, 14, 17,16,13 and 7. In the latter case they pass harmlessly notwithstanding the small resistance, since in this path four spark gaps-are traversed in series.

directly to ground. The resistances 16, 1 7

With

For the same reason, after the simultaneous operation of all the lightning arresters, no excessive passage of current can take place between the leads. 1

Instead of the auxiliar paths to ground being branched oll directly at the points of junction of the spark gaps withthe resistance; it is also possible, as shown in Fig. 2, to branch them off from intermediate points of the resistances, points located near the junction of each spark gap and its resistance. According to this arrangement the small resistances 16, 17 and 18 may be entirely disensed with. This arrangement, like that of ig. 1, furnishes for rapidly oscillating discharges a path which contains only small resistances in series with the safety device. This is 'the essential condition for rapid carrying 0H of such discharges, while, of course, resistances which might be arranged in parallel to the excessive potential safety deother number of phases, or direct current systems.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. The combination with the conductors of a polyphase-electrical system, of a resistance" and a safety device connecting each conductor with each other conductor of the system, and a low reactance ath to ground from the junction of each sa ety device and its corresponding resistance.

2. The combination with a lurality of line conductors, of a discharge pat therebetween including resistance, a second discharge path therebetween of low reactance to lnclude part of said first named path, and a ground connectionfor an intermediateYpointm said second path.

3. The combination with a plurality of line conductors, a resistance path therebetweenf including a spark gap, a second path of low a reactance also including said spark gap, and

a connection to ground from an intermediate point on said second path.

4. The combination with the three conductors of a three phase system, resistance paths arran ed in delta between said con-' ductors for t e discharge of abnormal potential of relativelylow frequenc a spark ga in each of said resistance at s, and a path to ground through each 0 said spark gaps but ofl'ering less reactance to high ire uency discharges than do the resistance pat is between hne conductors 5. The combination of a ground connection, a plurality of paths otlow reactance leading therefrom, and a connection from each of said paths to a line conductor of an electrical system: through a resistance, and a connection from each of'said paths to a second line conductor through a path of lower .reactance.

6. In a lightning arrester, the combination-of a ground connection, a plurality of spark gap paths leading therefrom, a plurality of line conductors of a polyphase system, a connection from each of said paths to a line conductor through a resistance, and a second connection to another line conductor through a path including aspark gap but having lower reactance.

- 7. The combination with a plurality of line conductors of an' electric system, of a discharge path'from one line conductor to another, said path including a high resistance 'and also a safety device, and a path to ground for each of said line conductors, said last named path including a safety device and a resistance much lower in value than that of said high resistance in the path between line conductors.

' In witness whereof, I have hereunto set my hand this 23rd day of February, 1907.

KARL KUHLMANN.

. Witnesses:

JULnJs RUMLAND, KARL MICKELSEN. 

